I was at Crested Butte in Colorado when the extreme skiing championships were being held there 2 years ago. You will find the experts at these events to talk to and watch.
I had the opportunity to chat with a couple of competitors. In addition to the usual helmet, they usually use a mouthpiece to protect their teeth and body armour - spine pad, shoulder pads with arm and elbow pads built in, and a pair of padded shorts.
They used wide, long skis with bindings to DIN 18 or so, set at about 16.
Balance is usually through the boots, but also depends on the angle of the terrain at the take-off point. The landing area is most important - needs to have a steeper angle depending on the drop height which reduces the force of impact on landing, and needs to have a lot of snow to absorb the impact, and sufficient runout to reduce speed after landing. Avoid landing on flatter terrain - there is a greater risk of spine and joint compression injuries.
Training should start with small jumps at low speed and involve progressive increases in drop height.